When to say when: can excessive drinking explain silicon uptake in diatoms?

Area of Science:

• Marine biology
• Biogeochemistry
• Cell biology

Background:

• Diatoms are key players in the oceanic silicon cycle and produce intricate silica cell walls.
• Understanding diatom silica biogenesis is crucial for nanotechnology applications.
• Silicon transporters are known, but the exact silicification mechanism remains unclear.

Purpose of the Study:

• To evaluate the bioenergetic feasibility of macropinocytosis for silicon uptake in diatoms.
• To assess if pinocytosis aligns with known diatom physiological constraints.

Main Methods:

• Bioenergetic calculations of cellular requirements for pinocytosis.
• Comparison of calculated requirements with established diatom physiology data.
• Analysis of diatom uptake kinetics, growth, and ultrastructure.

Main Results:

• Pinocytosis requires substantial bioenergetic, membrane recycling, and vacuolar volume.
• These requirements are inconsistent with current diatom physiological data.
• Calculated demands for pinocytosis exceed diatom cellular capacities.

Conclusions:

• Pinocytosis is not a viable primary mechanism for silicon uptake in diatoms.
• The proposed macropinocytosis model for silicon uptake is energetically unfavorable.
• Further research is needed to elucidate the true mechanism of diatom silicification.